Throughout the world, misuse of terminology related to the field of menopause has caused a great deal of confusion and misinformation among healthcare providers, those in research, the media, and the public. To help ensure a standardized definition of key words used in the field, the International Menopause Society (IMS) commissioned a project through its sub-organ, the Council of Affiliated Menopause Societies (CAMS).

The list of menopause-related definitions (see below) was approved by the Board of IMS on October 11, 1999, in Yokohama, Japan.

In most instances, agreeing on the appropriate definition was not controversial. However, there were differing opinions on maintaining the word climacteric in the medical lexicon. Unlike the definitions published by the World Health Organization (WHO), most committee members voted in favor of maintaining this word and the term climacteric syndrome, essentially because these words have been used for generations and are considered to be an accurate descriptive of this phase of life.

Definitions

Menopause (natural menopause) – the term natural menopause is defined as the permanent cessation of menstruation resulting from the loss of ovarian follicular activity. Natural menopause is recognized to have occurred after 12 consecutive months of amenorrhea, for which there is no other obvious pathological or physiological cause. Menopause occurs with the final menstrual period (FMP) which is known with certainty only in retrospect a year or more after the event. An adequate biological marker for the event does not exist. [Source: WHO]

Perimenopause – the term perimenopause should include the period immediate prior to the menopause (when the endocrinological, biological, and clinical features of approaching menopause commence) and the first year after menopause. [Source: WHO]

Menopausal transition – the term menopausal transition should be reserved for that period of time before the FMP when variability in the menstrual cycle is usually increased. This term can be used synonymously with "premenopause" although this latter term can be confusing and preferably should be abandoned. [Source: WHO]

Climacteric – The phase in the aging of women marking the transition from the reproductive phase to the non-reproductive state. This phase incorporates the perimenopause by extending for a longer variable period before and after the perimenopause. [Source: IMS]

Climacteric syndrome – the climacteric is sometimes, but not necessarily always, associated with symptomatology. When this occurs, it may be termed the "climacteric syndrome." [Source: IMS]

Premenopause – the term premenopause is often used ambiguously to refer to the one or two years immediately before the menopause or to refer to the whole of the reproductive period prior to the menopause. The group recommended that the term be used consistently in the latter sense to encompass the entire reproductive period up to the FMP. [Source: WHO]

Postmenopause – the term postmenopause is defined as dating from the FMP, regardless of whether the menopause was induced or spontaneous. [Source: WHO]

Premature menopause – ideally, premature menopause should be defined as menopause that occurs at an age less than two standard deviations below the mean established for the reference population. In practice, in the absence of reliable estimates of the distribution of age at natural menopause in populations in developing countries, the age of 40 years is frequently used as an arbitrary cut-off point, below which menopause is said to be premature. [Source: WHO]

Induced menopause – the term induced menopause is defined as the cessation of menstruation which follows either surgical removal of both ovaries (with or without hysterectomy) or iatrogenic ablation of ovarian function (e.g. by chemotherapy or radiation). [Source: WHO]